This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application for OPTICAL FIBER FOR LIGHT AMPLIFIER earlier filed in the Korean Industrial Property Office on Oct. 13, 1998 and there duly assigned Ser. No. 42713/1998.
1. Field of the Invention
The present invention relates to optical fibers for use in a light amplifier, and more particularly, to an optical fiber for use in alight amplifier which can be used at wavelengths of both 1.3 xcexcm and 1.55 xcexcm.
2. Description of the Related Art
The wavelength of light used in optical communications has shifted from the wavelength of 1.3 xcexcm to the wavelength of 1.55 xcexcm. In general, praseodymium ions (Pr+3) are used to dope an optical fiber used to amplify an optical signal having a wavelength of 1.3 xcexcm, while erbium ions (Er+3) are used to dope an optical fiber used to amplify an optical signal having a wavelength of 1.55 xcexcm.
U.S. Pat. No. 5,486,947, to Ohishi et al., entitled OPTICAL FIBER FOR OPTICAL AMPLIFIER, discloses an optical fiber for use in an optical amplifier, which is capable of operating with sufficient optical gain at the 1.3 xcexcm wavelength band. The optical fiber is a fluoride glass optical fiber containing rare earth metal ions in a core glass, wherein the refractive index difference between the core and a cladding layer is above 1.4%, and the glass contains lead difluoride (PbF2) in a proportion of 25 mol % or less based on the total composition for forming the glass. However, this fiber is designed for amplification of the 1.3 xcexcm wavelength band.
Now, both wavelengths of 1.3 xcexcm and 1.55 xcexcm are used in many optical communications related fields. Thus, different parts, that is, separate parts suitable for each wavelength, are required to construct a single optical circuit, and the costs of development and of switching devices from one wavelength to the other are high.
It is therefore an object of the present invention to provide an improved optical amplifier.
It is a further object of the invention to provide an optical device not requiring separate components for both the 1.3 and 1.55 xcexcm bands.
It is another object of the invention to provide an optical amplifier for both the 1.3 and 1.55 xcexcm bands which is less expensive.
It is still another object of the invention to provide an optical amplifier with improved amplification efficiency.
It is a yet further object to provide an optical fiber for use in an optical amplifier which can be used for both the 1.3 and 1.55 xcexcm bands.
It is yet another object to provide an optical glass which can be used in an optical amplifier for both the 1.3 and 1.55 xcexcm bands.
According to an aspect of the present invention, there is provided an optical fiber for an optical amplifier, which is formed by doping glass with rare-earth ions, wherein both praseodymium ions (Pr+3) and erbium ions (Er+3) are used as the rare-earth ions, and the glass is a fluoride glass or a sulfide glass. That is, the fiber is formed of a glass which is a fluoride or sulfide glass further as containing both Pr+3 and Er+3.
Preferably, the content of Pr+3 is in the range of approximately 100 to 1000 ppm by weight and the content of Er+3 is in the range of approximately 100 to 5000 ppm by weight. If the Pr+3 or Er+3 content is outside the above range, light amplification efficiency is undesirably lowered. Also, the mixing ratio of Pr+3 to Er+3, by weight, may be between 1:1 and 1:3. If the ratio of Pr+3 to Er+3 exceeds the above ratio, fluorescence emission quantity at the wavelength of 1.55 xcexcm is decreased. Conversely, if the ratio of Pr+3 to Er+3 is less than the above ratio, the amplification at the wavelength of 1.3 xcexcm is unfavorably decreased.